Glycolurils, which are heterocyclic compounds having four urea-based nitrogens in its ring structure, have been used in various applications and for production of new functional compounds, based on the reactivity of the urea-based nitrogens.
On the other hand, compounds having highly reactive functional groups, for example, allyl groups in a plural number in the molecule, such as triallyl isocyanurate, are well known as a crosslinking agent for synthetic resins and rubbers. Similarly, tetraallylglycolurils having four allyl groups in the molecule, which function as a crosslinking agent for synthetic resins and rubbers, are also known.
However, for example, glycoluril compounds of which the hydrogen atoms on all of the four nitrogen atoms are substituted with carboxyalkyl groups are expected to function as a crosslinking agent for epoxy resins and others, but no such compound is hitherto known. In addition, compounds having plural glycidyl groups in the molecule as functional groups, such as triglycidyl isocyanurate that has three glycidyl groups in the molecule, have been well known as a crosslinking agent for epoxy resins.
However, glycoluril compounds of which the hydrogen atom on at least one nitrogen atom is substituted with a glycidyl group, are not hitherto known.
Such glycoluril compounds of which the hydrogen atom on at least one nitrogen atom is substituted with a glycidyl group are useful as synthetic intermediates for oxygen-containing compounds; glycolurils having one epoxy group in the molecule are useful, for example, as reactive diluents for epoxy resins; and glycolurils having two or more epoxy groups in the molecule are expected to be useful, for example, as crosslinking agents for epoxy resins.
As described above, although tetraallylglycolurils are already known, glycolurils having one allyl group in the molecule, which are useful, as they are, for example, as synthetic intermediates, and allylglycolurils having two or three allyl groups in the molecule, which are expected to be useful as crosslinking agents for synthetic resins and rubbers, are not hitherto known.
Thus, the basic invention of the present invention relates to a new glycoluril having a carboxyalkyl, glycidyl or allyl group as the functional group. The present invention further relates to various useful resin compositions comprising a glycoluril having a carboxyalkyl, a glycidyl or an allyl group as the functional group that may partially include already known glycolurils.
Accordingly, the present invention provides the above-mentioned basic invention, and in addition, a first, a second and a third inventions which relate to resin compositions comprising the glycoluril having a carboxyalkyl, a glycidyl or an allyl group as the functional group. Hereinafter, the background of the first, second and third inventions will be described.
First Invention
In particular, the first invention of the present invention relates to the following two inventions:
(1) a new tetrakis(carboxyalkyl)glycoluril and its use, particularly as an epoxy resin composition comprising the tetrakis(carboxyalkyl)glycoluril as a crosslinking agent.
(2) a polyester resin composition for use in powder paints comprising the polyester resin obtained by polycondensation reaction of the above-mentioned tetrakis(carboxyalkyl)glycoluril with glycols.
Powder paints have advantages over solvent-type paints, for example, that they are pollution-free paint generating no organic volatile materials, give thick coated product in one application, permit use of the coated product immediately after coating, are relatively cheap, and can be recovered and reused. Thus, recently there are rapidly increasing demand for them as protective decorative paints for home electrical appliances, building materials, automobile parts and others.
Epoxy resin-, acrylic resin- and polyester resin-based paints have been mainly used as powder paints and, in particular, polyester resin-based powder paints provide coating film with favorably balanced performance.
It is needed for production of a powder paint superior in weather resistance to improve the weather resistance of the main component polyester resin, and normally, polyester resins having higher copolymerization ratios of isophthalic acid as a carboxylic acid component and neopentylglycol as a glycol component are used.
Since isophthalic acid has an absorption region different from the wavelength region of solar light energy and neopentylglycol has no hydrogen atoms at the β-carbons, polyesters containing larger amounts of these components are known to be resistant to photodegradation and show favorable weather resistance.
Isocyanate-based curing agents used in the polyester resin-based powder paints have hydroxyl groups at main terminals, and have a structure which is unreactive at a certain temperature or lower by blocking the highly reactive isocyanate group therein with a blocking agent; however, they contaminate a baking oven as the blocking agent dissociates when they are baked, and thus the use of them is not desired.
Although triglycidyl isocyanurate-based curing agents contain no blocking agent, they show mutagenicity and thus use of them is unfavorable from the point of safety.
Recently, hydroxyalkyl amides are attracting attention as a curing agent, replacing the triglycidyl isocyanurate curing agents. Powder paints containing a hydroxyalkyl amide as a curing agent permit low-temperature baking and give no volatile materials during baking. Thus, they are clean paints that have no load on environment.
However, powder paints containing a hydroxyalkyl amide as a curing agent has a disadvantage that they are lower in the smoothness and substrate adhesiveness of the coated film, in particular, in adhesiveness after water- and humidity-resistance treatments.
Although a powder paint of a polyester resin which is obtained from an aromatic dicarboxylic acid and an aliphatic diol, and has a particular viscosity and a particular acid value is proposed to overcome such disadvantages (see Patent Document 1), the powder paint does not show satisfactory weather resistance, though it is superior in smoothness and substrate adhesiveness of the coated film.
Also proposed is a powder paint comprising a resin which is obtained by depolymerization of a polyester resin from isophthalic acid and neopentylglycol with isophthalic acid as the main component (see Patent Document 2). However, the powder paint is still insufficient in smoothness of the coated film, though it is superior in weather resistance, low-temperature curing efficiency, smoothness of coated film and substrate adhesiveness.
Second Invention
A second invention of the present invention relates to a new glycidylglycoluril of which the hydrogen atom on at least one nitrogen atom is substituted with a glycidyl group and use of the same, particularly as an epoxy resin composition comprising the same.
Thus, the second invention of the present invention relates to the following four inventions:
(1) A New Glycidylglycoluril and a Resin Composition Comprising the Same
Glycolurils having glycidyl groups as functional groups are not hitherto known, and they are expected to be useful because of the reactivity of the glycidyl group.
(2) An Epoxy Resin Composition for Use in Sealing of Optical Semiconductor Elements
Generally, epoxy resin compositions obtained by using an epoxy resin such as bisphenol A epoxy resin and a curing agent such as an acid anhydride have been widely used recently as thermosetting resin compositions for sealing optical semiconductor elements such as light-emitting elements and light-receiving sensors because the cured products demand transparency.
However, recently under the trend toward higher brightness of light-emitting elements and use of light-receiving sensors in in-vehicle applications and as blue ray pickup, there is a growing demand for a thermosetting resin composition which provides a transparent sealing material superior in heat resistance or lightfastness to conventional materials.
Such being the case, for the purpose of improving the heat resistance or lightfastness of cured product from a thermosetting resin composition, there are proposed a method of raising the glass transition temperature (Tg) of cured product using a polyfunctional epoxy resin in the thermosetting resin, and also a method of suppressing photodegradation of cured product by light absorption using an alicyclic epoxy resin in the thermosetting resin (see Patent Document 3).
Examples of such epoxy resins used include triglycidyl isocyanurate. However, as the cured product from a thermosetting resin composition comprising triglycidyl isocyanurate is hard and brittle, there is caused a problem that the cured product may be cracked by heat shrinkage when the optical semiconductor element is resin-sealed. In addition, as triglycidyl isocyanurate is high in crystallinity, the thermosetting resin composition in the liquid form comprising triglycidyl isocyanurate has a problem that it inherently has not a sufficient pot life, for example, as the viscosity of the composition is increased by crystallization.
(3) A Thermosetting Resin Composition Comprising a Phenol Compound
Thermosetting resin compositions represented by epoxy resin compositions are superior in processability and the cured products therefrom show favorable electrical properties, heat resistance, adhesiveness, moisture resistance (water resistance) and other properties and thus, thermosetting resin compositions have been used widely in the fields of electric and electronic parts, structural materials, adhesives, paints and others.
However, recently along with the technical advances in the electric and electronic fields, there exists a demand for further improvement in the resins used as raw materials, for example, in purity, moisture resistance, adhesiveness and dielectric properties, and for low viscosity for higher filling efficiency of filler and high reactivity for shortening the molding cycle.
In applications for aerospace materials, leisure and sport devices, for example, light-weight materials superior in mechanical properties are demanded as structural materials.
In particular in the fields of semiconductor sealing and substrates (substrates and the associated materials), as reduction in size and weight and increase in functionality of electronic devices proceed further, LSI and chip components are integrated further more densely and the shape thereof is also changing rapidly toward higher pin count and smaller size. Thus, in the fields of printed wiring board, developments for fine wiring are under progress for improvement in mounting density of electronic parts.
A method of producing a printed wiring board that satisfies these requirements is a build-up method, which is becoming a mainstream method for reduction in weight and size and for finer wiring.
Under increasing environmental consciousness, there is also an activated movement toward establishment of regulations on materials, including electronic parts, possibly discharging hazardous substances during combustion. Bromine compounds have been used as flame retardants for conventional printed wiring boards, but these compounds may generate hazardous substances during combustion. Thus, the use of bromine compounds would be prohibited in the near future.
Lead-free solders are also being commercialized as the solders generally used for connection of electronic parts to printed wiring boards. The lead-free solders have a processing temperature approximately 20° C. to 30° C. higher than that of conventional eutectic solders, and thus, electronic parts should have a heat resistance higher than that of conventional ones.
A low-dielectric layer is formed on the surface of recent silicon chips for high-speed operation thereof and, as a result of the low dielectric layer formed, the silicon chips became very brittle. Conventional printed wiring boards have a thermal expansibility significantly different from that of silicon chips, and it is desired that the thermal expansibility of a printed wiring board is reduced to a value similar to that of a silicon chip for reliable connection of the printed wiring board to the silicon chip.
Generally, a method of decreasing the thermal expansibility of the entire insulation layer by adding a low-thermal expansibility inorganic filler thereto in a greater amount is employed to reduce the thermal expansibility of the printed wiring board (see, for example, Patent Document 4). However, such a method often gives many disadvantages such as deterioration of fluidity, deterioration of insulation reliability and others.
Thus, it is studied to achieve the low thermal expansion by properly selecting a suitable resin or by improving the resin. For example, in the case of an aromatic ring-containing epoxy resin, a resin composition for preparation of a low-thermal expansion insulating layer by pressure molding, which comprises an epoxy resin having a bifunctional naphthalene skeleton or a biphenyl skeleton, is proposed (see Patent Document 5); however, the resin composition comprises a filler in an amount of 80 to 92.5 vol %.
The thermal expansibility of a resin composition for wiring boards is generally reduced by a method of increasing the crosslinking density, raising the glass transition temperature (Tg) and thus lowering the thermal expansibility (see Patent Documents 6 and 7). However, it is needed to shorten molecular chain between functional groups for increase of crosslinking density, but it is difficult to shorten the molecular chain more than a particular length from the points of reactivity, resin strength and others.
In addition, an effort to introduce an imide skeleton, which is considered to be useful for higher heat resistance and lower thermal expansion, is also made and, for example, a build-up thermosetting resin composition comprising an imide group-containing aromatic diamine and an epoxy resin is proposed (see Patent Document 8). However, when a low-molecular weight polyimide compound is used as a curing agent for an epoxy resin, the resulting cured product is frequently not so much different in properties from the cured products of common epoxy resins.
(4) An Alkali-Developing Photocurable/Thermosetting Resin Composition
Generally, in printed wiring boards for use in electric products, a solder resist film is formed as a permanent protective layer on a substrate carrying a circuit of a conductor layer. The solder resist film is formed to prevent adhesion of solder on undesired regions in the soldering process for connecting (mounting) electric and electronic parts onto the printed wiring board and thus to avoid short circuiting of the circuit and protect the conductor layer.
Thus, properties such as adhesiveness to substrate and conductor layer, chemical resistance and insulating property are required for the solder resist film. As the resin composition giving a solder resist film satisfying these properties, a resin composition is known which can be developed with an aqueous alkaline solution (see Patent Document 9). However, the solder resist film obtained by curing the composition is not sufficiently flexible and has a problem that it is cracked during cutting process or during thermal shock test. Such a solder resist film with cracks does not play a role for insulation protection and may cause circuit breaking.
Resin compositions for flexible printed wiring board are also proposed (see Patent Documents 10, 11 and 12). However, solder resist films obtained by curing these compositions do not show sufficient flexibility. They also have a disadvantage that the solder heat resistance is lowered when the flexibility is improved and resin compositions with sufficient properties are yet to be proposed.
As described above, there exists a need for a resin composition giving a solder resist film that shows the basic properties demanded for solder resist film and is yet superior in flexibility and thermal shock resistance.
Third Invention
The third invention of the present invention relates to the following six inventions:
(1) A New Allylglycoluril
Compounds having plural highly reactive allyl groups in the molecule such as triallyl isocyanurate have been well known as a crosslinking agent for synthetic resins and rubbers. Similarly, tetraallylglycolurils having four allyl groups in the molecule, which function as a crosslinking agent for synthetic resins and rubbers, are also known (see Patent Document 13).
However, glycolurils having one allyl group in the molecule are useful, as they are, for example, as synthetic intermediates, and on the other hand, glycolurils having two or three allyl groups in the molecule are expected to be useful as crosslinking agents for synthetic resins and rubbers. However, these compounds are not hitherto known.
(2) An Olefinic Resin Composition
Olefinic resins that have favorable electric insulating property and solvent resistance, the various physical properties of which can be regulated, for example, by properly employing one of various crosslinking means such as radiation ray crosslinking, electron beam crosslinking, peroxide crosslinking, sulfur crosslinking and silane crosslinking with a silane compound, have been used widely in various fields including the fields of electric and electronic materials.
As described above, glycolurils, i.e., heterocyclic compounds having four urea-based nitrogen atoms in the ring structure, have been used in various applications and as intermediated materials for functional compounds, based on the reactivity of the urea-based nitrogen.
In particular, glycolurils having highly reactive allyl groups in the molecule are expected to be useful as a crosslinking agent for olefinic resins, based on the active allyl groups.
(3) A Curable Composition Superior in Adhesiveness
There are growing requirements on reliability against external environments such as light and heat in the fields of electronic and optical materials year by year. Thermosetting resins have been long used in these fields and, in particular, epoxy resins have been used widely, because of their flexibility in use and high adhesiveness to various substrates. However, they are insufficient, for example, as peripheral materials such as high-brightness light-emitting diodes and power semiconductors, from the viewpoints of long-term heat resistance and lightfastness. Glass has long been known as the material satisfying the heat resistance and lightfastness, but it also has a disadvantage that it is inferior in processability and substrate adhesiveness.
To overcome these disadvantages, organic-inorganic hybrid resins that are superior in heat resistance and lightfastness to organic polymer materials such as epoxy resins and superior in processability and adhesiveness to inorganic polymers such as glass have been used widely. In particular, thermosetting resins prepared by making use of hydrosilylation reaction, which is an addition reaction of a hydrosilyl group to a carbon-carbon double bond, are proposed (see, for example, Patent Documents 14, 15 and 16), and these resins are found to show favorable heat resistance, lightfastness and adhesiveness.
However, these resins are all insufficient from the viewpoint of optical transparency. Thus, it is difficult to apply these resins for use in optical material applications such as light-emitting diodes and display devices.
In contrast, in the case of a system having an isocyanuric acid skeleton as the organic component (see, for example, Patent Document 17), a composition which gives a thermosetting resin preserving the properties above and yet showing high transparency is proposed, but the composition has a high glass transition point, and thus has a disadvantage, for example, that, when it is coated on a substrate, the resulting film warps due to the strength of the heat stress and becomes less adhesive to the substrate.
A composition comprising a compound that has epoxy groups such as glycidyl groups as a component is proposed to overcome the problem (see, for example, Patent Document 18). However, it has a problem of trade-off relation that introduction of an epoxy group for expression of adhesiveness leads to deterioration in heat resistance and lightfastness.
Under the circumstances described above, there exists an urgent demand for a thermosetting resin which has favorable heat resistance, lightfastness and transparency, and in addition, shows smaller thermal stress, and is thus resistant to warping and superior in adhesiveness.
(4) A Thermosetting Resin Composition for Sealing Semiconductors, Comprising an Organopolysiloxane-Modified Allylglycoluril
Transfer molding using a mold, potting with a liquid sealant resin, screen printing or the like is performed to seal semiconductor devices with a resin. Recently along with reduction in size of semiconductor elements, electronic devices are required to be reduced in size and thickness, and it is needed to seal a thin package carrying silicon dies stacked thereon with a resin at a thickness of 500 μm or less.
In relation to the present invention, various applications of isocyanurate compounds similar to glycolurils are proposed.
Example of the known compositions comprising an isocyanurate ring-containing polymer and an isocyanurate ring-containing terminal hydrogen polysiloxane polymer include: compositions comprising an epoxy group ring-opening polymerizable polysiloxane composition obtained by addition reaction of diallyl monoglycidyl isocyanurate to a Si—H group-containing polysiloxane (see Patent Document 19), compositions comprising the isocyanurate ring-containing polysiloxane above and a Si—H group-containing polysiloxane (see Patent Document 20), addition-curable compositions comprising a triallyl isocyanurate and a Si—H group-containing polysiloxane (see Patent Document 21), addition-curable compositions comprising a polysiloxane having an isocyanurate ring and Si—H groups and an alkenyl group-containing cured product (see Patent Documents 22, 23 and 24) and the like.
However, although the isocyanurate ring-containing polymer composition described above, which contains siloxane bonds in the main agent, is flexible, it is lower in compatibility with a crosslinking agent. In addition, the site of the alkenyl group present is uncertain, and thus, it is difficult to cure the composition by addition reaction and thus to give the favorable characteristic (rapid curing reaction) of the hydrosilylation (addition reaction). The isocyanuric acid-containing polymer composition also has a disadvantage that it leads to high crosslinking density and is rigid and less flexible.
Under these circumstances, there is still no cured product prepared by addition reaction between an isocyanurate ring-containing polysiloxane and a Si—H group-containing polysiloxane that is superior in flexibility, curing properties and compatibility and also in steam permeation resistance.
(5) An Electron Beam-Curable Resin Composition
LED elements that are power saving and have longer lifetime are spreading recently as light sources replacing incandescent lightbulbs and others. Generally, when LED elements are used as a light source, plural elements are mounted on a metal substrate and a reflector is placed around them to improve the illuminance by reflection of light.
However, a device employing such a reflector has a disadvantage that it becomes less bright as the reflectance of the reflector lowers on account of deterioration of the reflector by the heat generated during light emission.
An electron beam-curable resin composition containing triallyl isocyanurate as the crosslinking agent for polyolefin resins has been proposed to overcome the disadvantage, and it is reported that it is possible by using such a resin composition to suppress the degradation of reflector device (see Patent Document 25). However, the triallyl isocyanurate used in the resin composition is highly volatile and has a disadvantage that the amount of crosslinking agent contained is reduced during the heat molding for preparation of the cured product.
(6) A Silicone Resin Composition
Use of an epoxy resin has been proposed as the resin in compositions for sealing optical semiconductors (see, for example, Patent Document 26). However, the sealed products prepared from such epoxy resin-containing composition have a disadvantage, for example, that they turn yellow by the heat generated by a white LED element.
Also having been proposed room temperature-curable organopolysiloxane compositions containing a two silanol group-containing organopolysiloxane, a silane compound having two or more hydrolyzable groups bound to the silicon atom in the molecule or the like, and an organic zirconium compound (see Patent Documents 27 and 28). Also having been proposed adding a condensation catalyst to a mixture of a two silanol group-containing diorganopolysiloxane or the like and a silane or the like having three or more alkoxy groups, and heating the resulting mixture (see Patent Documents 29 and 30).
However, as silicone resins are higher in gas permeability than epoxy resins and thus permit easier permeation of air, they have a disadvantage that the silver plate formed on optical semiconductor package is easily discolored by hydrogen sulfide in the air and, as a result, the optical semiconductor package shows a reduced brightness. Silicone resins are generally cured to increase sulfur resistance, but it leads to disadvantages of curing shrinkage as well as exfoliation thereof from LED package and breakage of wire by the shrinkage.